postgresql check if exists while executing prepared statement - php

Question

I'm preparing some statements and want to check if the row exists before I update. If it exists then update it, if it doesn't then output a message "No such animal". I have the update bit working, but unsure how to check if the row exists. Please assist.
$v = array();
$v[] = $_POST['status'];
$v[] = $_POST['id'];
$dbh = dbh_get();
$sql = 'UPDATE tap SET status=?
WHERE id =?';
$stmt = $dbh->prepare($sql);
$stmt->execute($v);
\\ if row isn't there display message "No such animal"
\\ otherwise print the below
printf("Status was changed to - %s", $v[0]);
\\then either way have my continue button for me to click on
print '<div class="button" style="float:left;" onclick="window.location.href=\'admin.php\';">Admin</div>' . "\n";
dbh_free($dbh)

Answer 1

According to your question, you want to check if the row exists before performing update. you can try this -
$id_exist = 0;
$sql = "SELECT id
FROM tap" ;
$sql_prepare = $dbh->prepare($sql);
$sql_prepare->execute();
while($row = $sql_prepare->fetchObject()) {
if($_POST['id'] == $row->id) {
$id_exist = 1;
}
}
if($id_exist == 1) {
// perform update here
} else {
echo 'No such animal';
}